Design of an Inexpensive Residential Phasor Measurement

Unit

Jeremy VickDepartment of Electrical and Computer Engineering

Union CollegeSchenectady, NY

Advisor: Professor Dosiek

November 25, 2014

Abstract

Phasor measurement units, (PMUs) are widely used by power companied to measure thestate of transmission lines and the quality of transmitted power. The goal of this project isto design a low cost PMU that takes measurements at the residential level of the power grid.This device must be easy to manufacture and highly reliable. It will communicate resultsback to a central database via the internet. Compliance with IEEE Standard C37.118.1 andC37.118.2 is required. The widespread introduction of an inexpensive PMU will increasethe data resolution available in Wide Area Monitoring Systems (WAMS), providing controlroom operators with a more accurate picture of the state of the power grid.

Contents

1 Introduction 51.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.3 Report Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 Background 72.1 Synchrophasor Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2 Previous Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Design Requirements 103.1 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.1.1 Step Down and Device Power . . . . . . . . . . . . . . . . . . . . . . 103.1.2 Analog Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.1.3 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.4 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.5 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.3 Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4 Design Alternatives 164.1 Component Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.1.1 Computing Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.1.2 GPS Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5 Preliminary Proposed Design 185.1 Evaluation Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.1.1 Timing Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185.1.2 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185.1.3 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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List of Figures

2.1 Phase calculation based on UTC reference . . . . . . . . . . . . . . . . . . . 82.2 Angle convention for synchrophasors . . . . . . . . . . . . . . . . . . . . . . 82.3 OpenPMU block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.1 rPMU block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.2 Anti-aliasing filter frequency response . . . . . . . . . . . . . . . . . . . . . 113.3 Data frame transmission order . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.1 schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2

List of Tables

3.1 Required synchrophasor reporting rates . . . . . . . . . . . . . . . . . . . . 123.2 Data frame organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.3 Summary of design requirements . . . . . . . . . . . . . . . . . . . . . . . . 15

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1

Introduction

1.1 Motivation

On August 14, 2003, North America suffered its largest blackout. Major 345 kV transmis-sion lines dropped out of service, unbeknownst to operators, causing a cascading outage thatextended across the Midwest, Northeast, and into Canada [1]. An investigation launchedby the North American Electric Reliability Corporation (NERC) found that the blackoutcould have been confined to a small region had operators known the status of overstressedand failing lines [2].

Since this catastrophe, steps have been taken to improve real-time, networked mon-itoring of America’s electrical transmission and distribution network, in order to enablesystem operators to predict and counteract or confine disturbances. Increased situationalawareness can also allow the dynamic calculation of maximum load ratings based on en-vironmental conditions. Overall, improved monitoring allows utilities to provide power tocustomers in a more efficient, more reliable, and safer way.

The installation of phasor measurement units (PMUs) provides a real time image ofoperating conditions. Increasing the number of PMUs improves the resolution of dataavailable to control room operators. It also creates the possibility for implementation ofautomatic control systems to correct disturbances or failures. However, these devices arecostly, approximately $43,400 per installation, and are hard to install [3]. They also requirededicated communication networks to feed data back to centralized processors, known asphasor data concentrators (PDCs).

PMUs can offer a new insight when installed at the distribution level of the power grid.The prevalence of distributed generation, smaller power plants that supply communitiesrather than regions, is increasing due to the fact that renewable power generation is bettersuited for communities. This increase causes an increase in dynamic events at the distribu-tion level, as wind turbines and solar farms increase and decrease their output in step withthe weather. Having PMUs measuring at the distribution level will give a more accurate

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picture of how the increase in distributed generation affects the power grid on a day-to-dayand long term basis.

1.2 Objective

The goal of this project is to design a low cost PMU that takes measurements at theresidential level of the power grid. This device should be easy to manufacture and highlyreliable. It should communicate results back to a central database using the protocoldescribed in the IEEE Standard for Syncrophasor Data Transmission.

1.3 Report Structure

This report is divided into four major sections: an introduction and background sectionthat provides an overview of the issues the device intends to solve and enumerates theprevious work on PMUs, a detailed review of the design requirements, a summary ofdesign alternatives illustrating their merits and faults, and a comprehensive presentationof the preliminary proposed design for the project.

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2

Background

2.1 Synchrophasor Definition

Alternating Current (AC) is mathematically represented by a cosine wave,

x = A cos(2πfACt+ φ) (2.1)

where fAC = 60Hz in North America. Using a technique proposed by Charles ProteusSteinmetz in [4], AC can be represented as a simplified quantity called a phasor. Whenrepresenting a cosine as a phasor, it is assumed that the frequency of the signal remainsthe same. Therefore, the variable quantities are magnitude and phase. For AC, magnitudeis commonly defined as the root mean square of voltage. Equation (2.1) becomes

X =A√2φ (2.2)

Establishing phase requires either a signal or time reference. Synchrophasors calculatephase using an absolute time reference, commonly Coordinated Universal Time (UTC).Figure 2.1 shows a cosine superimposed on a UTC time pulse. The synchrophasor is definedto be 0◦ if the cosine has a maximum during the pulse and 90◦ if the cosine has a zerocrossing at the pulse. Values between 0◦ and 90◦ are calculated according to the selectedphasor estimation algorithm [5]. Previously, phasor measurement at generators and nodesin the transmission network was impractical due to geographic separation between thetwo. Implementation of synchrophasors allows for easy calculation of magnitude and phasedifferences between nodes based off a shared standard time.

2.2 Previous Work

The concept of a synchrophasor was first introduced in the 1980s and has since generateda large body of commercial and academic research. It is impossible to address all work

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Figure 2.1: Phase calculation based on UTC reference. Source: [6]

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 4, OCTOBER 2008 1805

Exploring the IEEE Standard C37.118–2005Synchrophasors for Power Systems

K. E Martin, D. Hamai, M. G. Adamiak, S. Anderson, M. Begovic, G. Benmouyal, G. Brunello, J. Burger,J. Y. Cai, B. Dickerson, V. Gharpure, B. Kennedy, D. Karlsson, A. G. Phadke, J. Salj, V. Skendzic, J. Sperr,

Y. Song, C. Huntley, B. Kasztenny, and E. Price

Abstract—IEEE Standard 1344–1995 [1] on measurement ofsynchronized phasors of power system currents and voltages hasbeen revised and published as IEEE Standard C37.118–2005 [2].This paper has been prepared by the IEEE Working Group whodeveloped the revised version. The purpose of the paper is toacquaint the power engineering community of the availability andcontent of this new standard, highlight some of the key differencesbetween the old and new versions, and introduce several applica-tions of this powerful technology.

Index Terms—Global positioning system (GPS) synchronizedphasor, phasor measurement unit (PMU), power system measure-ments, synchrophasor, wide-area measurements.

I. C37.118-2005 SYNCHROPHASOR STANDARD

T HIS section provides an overview of the new IEEE Stan-dard C37.118-2005, and summarizes its main points. The

standard was approved in September 2005 and published inApril 2006. It is available from IEEE in either PDF or printedform.

A. Overview

The standard covers synchronized phasor measurementsused in electric power systems. It defines the measurementconvention, provides a method of determining the precisionof measurements, and provides requirements for measurementperformance under steady state conditions. It also defines datacommunication formats for real-time data transmission. Thedocument introduces the concept of a phasor measurement unit(PMU)—a device making, communicating, and potentiallystoring these synchronized measurements. Compliant PMUsshould be interchangeable with each other by providing equiv-alent measurements when supplied with identical steady-stateinput signals, and communicating these measurements in astandardized way.

B. Basic Concept of a Synchrophasor

Synchrophasors, or synchronized phasor measurements,provide a means of referring the phasor representation of a

Manuscript received June 5, 2007. First published April 3, 2008; current ver-sion published September 24, 2008. Paper no. TPWRD-00320-2007.

Working Group H-11 of the Relay Communications Subcommittee of theIEEE Power System Relaying Committee.

This work was prepared by Working Group H-11 of the Relay Communi-cations Subcommittee of the IEEE Power System Relaying Committee of thePower Engineering Society.

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPWRD.2007.916092

Fig. 1. Synchrophasor definition and angle convention.

power system voltage or current to an absolute time reference.This absolute reference is provided in the form of a commontiming signal by high-accuracy clocks synchronized to coordi-nated universal time (UTC) such as the universally used globalpositioning system (GPS).

Using the synchronized clocks as a reference, a PMU cre-ates the phasor representation (complex number) of a constantsinusoidal signal as shown in Fig. 1. The reporting instant, rep-resented by a timetag, defines the reference for the phasor rep-resentation of the measured sinusoidal input. The relationshipbetween the reporting instant and the phasor representation issuch that the phase angle of the phasor is equal to the angularseparation between the reporting time and the peak of the sinu-soid. For example, in Fig. 1(a), the peak of the signal coincideswith the timetag yielding the angle measurement of 0 , while inFig. 1(b), the signal crosses zero at the timetag yielding ameasurement in accordance with the synchrophasor standard.

Determined with respect to an arbitrary timing signal, thephasor angle by itself has no particular significance. However,if all PMUs use the same timing reference, their measurementsare comparable, and the phase angle differences between pha-sors are accurate. As most applications seek to know the phaseangle differences between various phasors, the PMU output pro-vides an invaluable input to monitoring, protection, and controlfunctions in a power system.

C. Requirements for Compliance

Compliance with IEEE Standard C37.118 requires makingphasor measurements that meet the synchrophasor definition

0885-8977/$25.00 © 2008 IEEE

Figure 2.2: Angle convention for synchrophasors. Source: [7]

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Figure 2.3: OpenPMU block diagram. Source: [10]

on synchrophasors and their applications in the scope of this project so emphasis will beplaced on development of inexpensive PMUs.

K. Kirihara, B. Pinte, and A. Yoon designed and tested a relatively low cost (approx-imately $1050) PMU as part of an undergraduate senior project described in [8]. Theirproject utilized a National Instruments sbRIO for digital filtering and calculation of syn-chrophasors. Global Positioning System (GPS) was used to generate the time reference.The project was able to successfully measure phasors, but utilized only the National Elec-trical Code residential voltage standards to test the PMU, ignoring IEEE C37.118.1-2011.The group also did not address the transmission of synchrophasors to a centralized serveror phasor data concentrator (PDC).

In Brian Miller’s Masters thesis [9], alternatives for conventional current transducersare considered. Miller also examines the use of wireless networks for time synchronizationunder the IEEE 1588 standard. Use of wireless networks is found to provide a viablealternative to GPS synchronization, useful in areas where signal strength is diminished.It would also provide a cost reduction due to the elimination of the GPS module. Theseproposed changes were found to be viable improvements while remaining compliant withthe IEEE C37.118.1 standard.

In order to lessen the restrictions of proprietary hardware and algorithms on theprogress of PMU development, the OpenPMU [10] group was formed, dedicated to de-signing ”open source platform for synchrophasor applications and research.” The grouputilizes a standard data acquisition device (DAQ) from National Instruments and a GPSreceiver from Garmin as the basis for the OpenPMU. A PIC from Microchip synchronizesthe DAQ to the GPS timecode. The OpenPMU uses the Python scripting language run-ning on Microsoft Windows. It is currently able to measure synchrophasors, but has yetto achieve full compliance with IEEE C37.118.1.

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3

Design Requirements

3.1 Performance

A vast majority of the performance requirements for this project are drawn from the IEEEStandard for Synchrophasor Measurements for Power Systems [11], its 2014 amendment[12] and the IEEE Standard for Synchrophasor Data Transfer for Power Systems [13].Two classes of performance are laid out in the standards: P, for fast response with noexplicit filtering and M, for analytic measurements sttausceptible to aliasing. Adherenceto these standards will ensure that the device is compatible with existing phasor dataconcentrators (PDCs) and visualization software.

The device is broken down into seven different component parts as shown in Figure3.1. The measurement source is a 120v residential outlet. A step down circuit lowersthe voltage of the measurement source into the range of the A/D converter. This circuitwill also provide DC power for the device itself. An analog anti-aliasing filter will beused to limit the signal bandwidth before sampling. The signal passes through an A/Dconverter that samples in synchronicity with the time source. The time source providesan absolute time reference to the A/D converter and the Synchrophasor Estimator. TheSynchrophasor Estimator will calculate the magnitude of digital signal and run it througha phase estimation algorithm (PEA). The resulting magnitude and phase estimation willbe given a time tag and sent to a PDC via the internet interface. The device must alsoaccept commands transmitted by the PDC.

3.1.1 Step Down and Device Power

Analog to Digital (A/D) converters are not typically capable of measuring signals at 120v,meaning a voltage step down circuit must be designed to reduce the magnitude of the ACsignal to match the specified range of the A/D. The device may only have one connection tothe power source, meaning the step down circuit must also include a tap and rectificationcircuit to provide power for the chosen processor. The supply circuit should have over-

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Step Down

Anti-Aliasing Filter

120v Residential Outlet

A/D Converter

Time Source

Synchrophasor Estimator

InternetInterface

Data Concentrator

Control Commands

Device Power

Phasor DataConcentrator

OR

Figure 3.1: rPMU block diagram.

Figure 3.2: Anti-aliasing filter frequency response. Source: [14]

voltage protection to prevent damage to the device and have an output voltage ripple thatmeets the constraints of the chosen processor.

3.1.2 Analog Filtering

Since an A/D conversion is being performed, it necessary to have an analog low-pass filterto reduce the bandwidth of the input signal and eliminate aliasing. The cutoff frequency forthe low-pass filter should be just above fs/2, the chosen sampling frequency. The desiredfrequency response, defined in terms of the sampling frequency, is shown in Figure 3.2.

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System Frequency 50 Hz 60 Hz

Reporting Rates (frames per second) 10 25 10 12 15 20 30

Table 3.1: Required synchrophasor reporting rates. Source: [?]

3.1.3 Timing

Synchrophasors must, by definition, be recorded with respect to an absolute time reference.The absolute reference used by IEEE C37.118.1 is Coordinated Universal Time (UTC).UTC can be obtained from either a GPS receiver or through the internet based PrecisionTime Protocol (PTP) [15]. The time must be accurate within ±26µs according to thestandard. Receiving UTC via the internet is more practical for the scope of this project,as GPS signals can be very weak indoors. However, testing is needed to confirm thatsynchronization with internet time servers can be achieved with sufficient accuracy.

Each synchrophasor must be given a time tag according to Coordinated UniversalTime (UTC). The time tag consists of three numbers: a System On a Chip (SOC) count,a fraction-of-second count, and a time status value. SOC is specified as a 4-byte binarycount of the number of seconds since the Unix epoch, 00:00 January 1, 1970. Occasionally,a leap second must be inserted to keep SOC synchronized with UTC, which is specifiedusing a special case of the fraction-of-second as specified in section 4.3 of [11]. Time statusindicates the reliability of the clock, which can become unsynchronized due to loss of signal.Values for time status are specified in Table 6 of [11].

3.1.4 Measurement

Synchrophasor measurements must be synchronized with the time code source so they canbe time-aligned with measurements from other PMUs by a PDC. Reporting rates are alsodefined in IEEE C37.118.1 to ensure that multiple PMUs will take measurements at thesame rate.

Reporting Rate

The reporting rate, measured in phasors per second, must be a factor of the nominal systemfrequency. Required rated are listed in Table 3.1. The reporting rate must be selectableby the user via the device’s internet interface according to the protocol defined in [13].

Phase Estimation

There are two categories of phase estimation algorithms (PEAs): time domain and fre-quency domain. An example of a time domain PEA is the Weighted Least Squares method.WLS uses a Taylor series expansion of the signal to determine the phase. In [16], variation

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Figure 3.3: Data frame transmission order. Source: [13]

of the number of terms in the series is studied in an attempt to reduce error. The Interpo-lated Discrete Fourier Transform (IpDFT) is an example of a frequency domain algorithm.The IpDFT is significantly faster than WLS, but does not perform as well when distur-bances occur. A thorough comparison between WLS and IpDFT is carried out in [16]. Theselection of the PEA will provide the constraints for selection of a processor.

Total Vector Error

Total Vector Error (TVE) is a measurement of the difference between a perfect theoreticalphasor and the actual phasor measured by the PMU. The IEEE Std. C37.118.1 definesTVE as:

TV E(n) =

√(X̂r(n)−Xr(n))2 + (X̂i(n)−Xi(n))2

Xr(n)2 +Xi(n)2(3.1)

Where X̂r(n) and X̂i(n) are the real and imaginary components of the measured phasorand Xr(n) and Xi(n) are the components of the theoretical phasor. The standard specifiedthat TVE must be less than 1%. Sources of TVE include timing inaccuracy, off-nominalsignal frequency, and low frequency oscillations.

3.1.5 Communication

Communication between the PMU and PDC will take place via the internet. Data packetswill be sent using Transmission Control Protocol (TCP). Data packets are subdivided intoframes, each containing a specific piece of data. The frames required for sending phasordata, as defined in IEEE C37.118.2, to a PDC are listed in Table 3.2. The phasor itselfis transmitted in frame 7. The DIGITAL frame can be used to transmit extra devicestatus indicators not included in the STAT frame, relay statuses, breaker statuses or otherinformation. The generic order of frame transmission is shown in Figure 3.3, where DATA1,DATA2, etc. are frames 7-11 from Table 3.2

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No. Field Size (bytes) Description

1 SYNC 2 Sync byte followed by frame type and versionnumber.

2 FRAMESIZE 2 Number of bytes in frame.3 IDCODE 2 PMU ID number.4 SOC 4 Second Of Century time stamp.5 FRACSEC 4 Fraction of Second and Time Quality.6 STAT 2 PMU status flags.7 PHASOR 4 Phasor estimate. May be single phase or

3-phase positive, negative, or zero sequence.8 FREQ 2/4 Frequency.9 DFREQ 2/4 Rate Of Change Of Frequency.10 ANALOG 2+ Analog data, available for extra features.11 DIGITAL 2+ Digital data, available for extra features.12 CHK 2 Cyclic redundancy check (CRC-CCITT)

Table 3.2: Data frame organization. Source: [13]

3.2 Safety

The device must comply with the National Electric Code regulations for connection spacingand insulation for 120v connections [17]. The connection to the wall outlet should be madewith a NEMA 5-15 compliant connector as it is the most common outlet found in residences.The connector is rated for a maximum voltage of 125v, sufficient for the requirements ofthis project.

3.3 Cost

Commercial PMUs cost an average of $43,400 per installation [3]. This device will be in-stalled en masse in residences and should have a cost commensurate with mass production.The target cost for this project is under $1,000.

3.4 Summary

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Section Comments

Step down Step down 120v measurement source toacceptable range for A/D converter

Device power Determined by the choice of processorAnalog filtering Low pass filter with fc just above fs/2Timing Either internet or GPS basedPhase estimation Either WLS or IpDFTSafety Must follow all regulations for 120v wiring and

terminal spacingCost Target cost is under $1000

Table 3.3: Summary of design requirements

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4

Design Alternatives

4.1 Component Selection

4.1.1 Computing Platform

The computing platform is the core of the phasor measurement unit. It is responsible foracquiring raw AC voltage waveform data from an Analog to Digital Converter (ADC) insynchronicity with the GPS Pulse Per Second (PPS) time code, computing the magnitudeand phase of the signal, packaging the measured data into the IEEE C37.118.2 transmissionformat and sending the resulting data packet over the internet to a PDC. Many optionswere considered in the choice of the computing platform for this project, including the well-known Raspberry PI, the Arduino, BeagleBone Black, and Intel Edison. The RaspberryPI, while it is a relatively powerful platform with thorough documentation and an activeuser base, was dismissed due to the lack of an onboard ADC. Choosing a platform with anonboard ADC is important because it simplifies the circuitry and reduces the cost of thedevice. An Arduino, while it has an onboard ADC, lacks the computing power of the otherSOC based alternatives, requires additional components to connect to the internet, anddoes not have the ability to be reprogrammed remotely, an important consideration whendeploying a device in the homes of laymen residents. Intel’s Edison platform was consid-ered for its high computing power density (dual core 500 MHz processor), but ultimatelyrejected due to the scarcity of publicly available documentation. Ultimately, the Beagle-Bone Black was chosen as it has a number of advantages over the other contenders. It hasa 1 GHz processor, which outperforms the Raspberry PI’s 700 MHz, a built in ethernetport for internet connection, and an onboard ADC with eight input channels. The Blackalso can run the Debian or Ubuntu Linux distributions. Using these Linux distributionsprovides built in access to remotely update the device and a large package database to pullfrom when implementing components of the project. Of the most consequence in choosingthis board was the NEON and PRU subsystems. The NEON subsystem provides hard-ware acceleration for floating point calculations and a implementation of the Fast Fourier

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Transform that utilizes this capability has already been developed. Utilizing this librarywill allow for the reduction of the computational load on the processor, which in turn shouldenable the device to achieve a higher reporting rate. The PRU (Programmable RealtimeUnit) is significant because all of the instructions available in this subsystem have a fixedexecution time of three nanoseconds. The PRU interfaces directly with the ADC and theBlack’s onboard memory registers, meaning it can acquire data from both the GPS andAC voltage inputs to the ADC and store it for processing in a known amount of time thatcan be easily compensated for in the final calibration of the device.

4.1.2 GPS Module

As stated in the Timing section of the Design Requirements, the time source must beaccurate within ±26µs in order to achieve the accuracy specified in [11]. There are manytiming-specific GPS modules on the market, but their average price is $450, [?] which isprohibitive for the budget of this project. The Adafruit Ultimate GPS Module is offeredat a reasonable $40 and achieves ±9µs accuracy [?] on its PPS output. Though this is notas accurate as timing-specific sources, some boast sub ±5µs accuracy, [?] it is well withinthe specifications and budget of the device.

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5

Preliminary Proposed Design

5.1 Evaluation Plan

5.1.1 Timing Accuracy

Acquiring a highly accurate time source, such as an atomic clock, to test the accuracy ofthe timing circuit is impractical, due to the cost of such devices. However an indirect testcan be performed to analyze the stability of the timing circuit. Measuring the period ofthe pulse per second signal provided by the timing source over sixty minutes will give agood indication of the short term stability of the time source and local oscillator.

5.1.2 Measurement

The reference conditions for each testing parameter, as specified in section 5.5.4 of IEEEC37.118.1, are listed below. Each parameter should remain constant, unless it is currentlybeing tested.

• Voltage at nominal

• Current at nominal

• Frequency at nominal

• Voltage, current, phase, and frequency constant

• All interfering signals < 0.2% of the nominal frequency (60Hz)

• Temperature 23◦ ± 3◦C

• Humidity > 90%

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Figure 5.1: Circuit schematic of preliminary proposed design.

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Synchrophasor Estimation

Synchrophasor estimation should be tested by calculating the TVE as defined in (3.1) foreach testing condition listed in Table 3 of [11]. The TVE should remain below 1% in alltesting conditions. The signal generator and oscilloscope must have a testing uncertaintyratio of 4, i.e. for desired TVE of 1%, the devices should be able to measure TVE within±0.25%.

5.1.3 Communication

Confirmation of the proper communication protocol specified in IEEE C37.118.2 will beverified using the PMU Connection Tester software package provided by the Grid Protec-tion Alliance1. If necessary, the Wireshark filter for IEEE C37.118 communication may beused to examine the raw data frames2.

5.2 Summary

The goal of this project is to design an inexpensive residential phasor measurement unit.Designing an inexpensive PMU will allow the proliferation of real-time, networked moni-toring devices across the grid. Doing so increases the resolution of data available to controlroom operators and regional administrators. This will allow for the design of automaticcontrol systems that can react faster than control room operators to counteract and confinedisturbances on the grid.

The device will be entirely self contained, with the only external connections to theinternet and the residential wall outlet. There should be no interaction between the residentof the house and the device, initial installation will be done by the power company. Thedevice will be designed in compliance with the IEEE Std. C37.118, in order to ensurecompatibility with existing phasor data concentrators and visualization software.

Having an inexpensive PMU on the market opens up many possibilities for futuredevelopment and supports some of the objectives of the smart grid. In particular, it willsupport increased use of distributed generation. Distributed generation allows for the useof small, sustainable sources to supplement or be the sole power source of small areas. Thiscapability is key to the spread of sustainable power.

1The software can be found at http://pmuconnectiontester.codeplex.com2A more detailed summary of the filter can be found at http://www.wireshark.org/docs/dfref/s/synphasor.html

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Bibliography

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[2] NERC, “NERC Final Blackout Reccommendations,” North American Energy Relia-bility Corporation, Tech. Rep., 2004.

[3] U. D. of Energy, “Synchrophasor technologies and their deployment in the recoveryact smart grid programs,” Online, August 2013.

[4] C. P. Steinmetz, “Complex quantities and their use in electrical engineering,” in Pro-ceedings of the International Electrical Congress Held in the City of Chicago, August21st to 25th, 1893. American Institute of Electrical Engineers, 1894, pp. 33–74.

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